Exercise Tested Against Breast Cancer

Text: Annika Lund, first published in Medicinsk Vetenskap nr 1 2024 / Spotlight on breast cancer.

Does exercise protect against breast cancer?

“You have to keep your tongue in your mouth here (jag har googlat. Det verkar heta så även om jag tycker det later konstigt). There are population studies that show that among women who exercise, breast cancer is less common than among women who do not exercise. And when breast cancer has developed, those who exercise are less likely to have a recurrence than those who do not. But maybe this could be explained by other protective factors might be more common among women who exercise. It is not possible to prove causality in a population study”.

Does it matter how the exercise is done?

“It seems that a little more intense exercise is required, where you get your heart rate up and get sweaty”.

What is known about possible mechanisms?

“There is some knowledge that comes from animal studies. Mice that have wheels to run on have less tumor growth than mice without wheels to run on. Much of the effect is thought to be mediated through the immune system. There are also studies suggesting effects via the hormonal system”.

You will lead a study on exercise in cancer. Tell us about it!

“The study will include 712 women with breast cancer who are treated with chemotherapy before surgery. These are usually women with slightly larger tumors or more aggressive disease. Half of them will excercise according to a plan we have developed. This means at least 120 minutes of high-intensity training per week of increasing intensity level via an app plus 150 minutes per week of optional training of at least moderate intensity level. The other half will exercise as they are used to, but patients who already have a high level of exercise will not be included in the study. What we will mainly look at is the proportion of patients in both groups who have what is called a pathological complete response, i.e. the tumor is no longer present when the pathologist examines the removed tissue from the breast. Our hypothesis is that such a strong response to chemotherapy will be more common in the group with the exercise intervention”.

If you can show this, what are the implications for breast cancer care?

“Today, exercise is seen as a supportive treatment that improves well-being. But if we can show that exercise also affects the tumor disease itself, then it should be seen as an important part of the oncological treatment. Then we need to roll out exercise programs in all hospitals where breast cancer patients are treated. Then we need to think about whether exercise should be provided as a group training or via apps with support from physiotherapists. But – and this is important – we are only looking at how effective exercise is as a complement to other treatments. Exercise alone cannot cure breast cancer”.